Impasta

im-past-a (noun)

A piece of pasta found with other pasta noodles that do not share its type.

A test spy that can impersonate a given class and/or track methods passed to it.

Origin: portmanteau of imposter and pasta

protip: definition #2 is the one we're talking about

Installation

Add this line to your application's Gemfile:

gem 'impasta'

And then execute:

$ bundle

Or install it yourself as:

$ gem install impasta

Usage

It's pretty easy, to create a new Impasta just do:

imp = Impasta.decoy

You can give it a name too:

aka_imp = Impasta.decoy aka: 'totally not an imposter'

Both of those Impastas will accept any method and args you throw at them.

imp.whatever                       #=> self
aka_imp.lulz 2, 3, :slimpickins    #=> self

But you can also constrain the methods Impasta objects accept by passing in a target:

array_imp = Impasta.infiltrate target: Array.new

array_imp.first         #=> self
array_imp.johnnycarson  #=> raises Impasta::MissingMethod

You can also extract information from an instance of Impasta:

array_imp.impasta.ledger            # will display all methods sent to it in this format: [[method_name, arguments_sent_to_method, block_passed_to_method], ...]
array_imp.impasta.target            #=> [] # (this is the same array passed in earlier)
array_imp.impasta.origin            #=> "readme.rb line #54" # this will display where the Impasta was instantiated

Meet the Spies

Decoy

Impasta.decoy aka: "A type of dummy object"
It responds to any message with self! (ignores any target and does its own thing)
Excellent placeholder when you don't care about enforcing which methods can be called.

Wiretap

Impasta.wiretap aka: "A type of proxy object"
Passes method calls on to the target and returns exactly that.
Good to keep an eye on what your objects are talking about when you're not looking.

Infiltrate

Impasta.infiltrate aka: "A type of test double"
Responds with self (the Infiltate object) for any message the target recognizes, raises an exception for anything else.
Will raise for everything if no target provided!
Good for enforcing API integrity, if you can use this one instead of a Decoy, I highly recommend it.

Ghoul

Impasta.ghoul aka: "A type of null object"
Responds with nil for any message the target recognizes, raises an exception for anything else.
Like Infilitrate, but returns nil instead for situations where you need to test nil-resiliency or stop returning endless selfs.

Forging Messages (AKA: Mocking & Stubbing Methods)

Decoy and Infiltrate Impastas will always return self for any method they accept (any for Decoy, only what the target does for Infiltrate).
Ghoul always returns nil.
Wiretap always returns the same thing as the target.

But what if they didn't?

Enter: FORGERY

imp.decoy
tmp.identity                                     #=> self
imp.impasta.forge :identity, returns: "fake id"
imp.identity                                     #=> "fake id"

You can use a single returns keyword as above or you can use a block instead to set the value it will respond with when it receives the message. Arguments are ignored by the forgery, but you can check the ledger to make sure they are correct.

Secrets

All spies have secrets, you've already interacted with them above, obtained by calling the Spy#impasta method.

But they can do other things, here are a few more:

secrets.inspect_target to remind yourself about who this spy is targetting
secrets.inspect_forgeries to see the list of forgeries this spy is carrying
secrets.codename to get the spy to spill the beans on everything it knows
secrets.within accepts a block and executes in the context of the Impasta::Secrets instance, good for configuring a bunch of things all at once

Contributing

Fork it ( http://github.com/acook/impasta/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

acook/impasta